| Abstract: | Pure sand and gravel qualities are becoming to be rare resources and technical goods of increasing strategic importance for various industrial branches worldwide. Quartz sand as a crystalline raw material is chemically transformed into intermediates for the final production of synthetic amorphous silicon dioxides (SAS). Precipitated SAS are produced by chemical reaction of sodium silicates. Chlorosilanes are produced by reaction of silicon and ferrosilicon with HCl. They are used to produce pyrogenic SAS. High‐resolution transmission electron microscopy is needed to reveal the fine structure of these amorphous materials. Pyrogenic and precipitated SAS show a similar nanostructure as silica‐gels and ‐aerogels. Differences in amorphicity and short range order in finely divided, alkaline‐free, amorphous SAS on the one hand and in alkaline‐containing amorphous SiO2‐networks such as solid sodium silicates on the other still are not completely clarified. |
